1-phenyl-2-pyridinyl alkyl alcohol compounds as phosphodiesterase inhibitors

ABSTRACT

1-Phenyl-2-pyridinyl alkyl alcohol compounds are effective as inhibitors of the phosphodiesterase 4 (PDE4) enzyme and may be used to prevent and/or treat certain diseases or conditions.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 13/618,346, filed on Sep. 14, 2012, which was a continuation ofU.S. patent Ser. No. 12/700,926, filed on Feb. 5, 2010, now U.S. Pat.No. 8,440,834, and claims priority to European Patent Application No.09001660.1, filed on Feb. 6, 2009, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to inhibitors of the phosphodiesterase 4(PDE4) enzyme. More particularly, the invention relates to1-phenyl-2-pyridinyl alkyl alcohol compounds, which are useful asinhibitors of the phosphodiesterase 4 (PDE4) enzyme. The presentinvention also relates to processes for the preparation of suchcompounds, compositions which comprise such a compound, and combinationsof such compounds. The present invention further relates to therapeuticuses of such compounds.

2. Discussion of the Background

Airway obstruction characterizes a number of severe respiratorydiseases, including asthma and chronic obstructive pulmonary disease(COPD). Events leading to airway obstruction include oedema of airwaywalls, increased mucous production and inflammation.

Drugs for treating respiratory diseases such as asthma and COPD arecurrently administered through inhalation. One of the advantages of theinhalatory route over the systemic one is the possibility of deliveringthe drug directly at site of action, avoiding any systemic side-effects,thus providing a more rapid clinical response and a higher therapeuticratio.

Inhaled corticosteroids are the current maintenance therapy of choicefor asthma and together with bronchodilator β₂-agonists for acutesymptom relief, they form the mainstay of current therapy for thedisease. The current management of COPD is largely symptomatic by meansof bronchodilating therapy with inhaled anticholinergics and inhaledβ₂-adrenoceptor agonists. However, corticosteroids do not reduce theinflammatory response in COPD as they do in asthma.

Another class of therapeutic agents which are under investigation inview of its anti-inflammatory effects for the treatment of inflammatoryrespiratory diseases such as asthma and COPD is represented by theinhibitors of the phosphodiesterase enzymes (PDEs), in particular of thephosphodiesterase type 4 (hereinafter referred to as PDE4).

Various compounds acting as PDE4 inhibitors have been disclosed.However, the usefulness of several PDE4 inhibitors of thefirst-generation such as rolipram and piclamilast has been limitedbecause of their undesirable side effects such as nausea, gastric acidsecretion and emesis due to their action on PDE4 in the central nervoussystem and due to the action on PDE4 in parietal cells in the gut.

The cause of said side effects has been widely investigated. It has beenfound that PDE4 exists in two distinct forms representing differentconformations, that were designated as high affinity rolipram bindingsite or HPDE4, especially present in the central nervous system and inparietal cells, and low affinity rolipram binding site or LPDE4 (see,Jacobitz, S et al., Mol. Pharmacol., 1996, 50, 891-899), which is foundin the immune and inflammatory cells. While both forms appear to exhibitcatalytic activity, they differ with respect to their sensitivity toinhibitors. In particular, compounds with higher affinity for LPDE4appear less prone to induce side-effects such as nausea, emesis andincreased gastric secretion.

The effort of targeting LPDE4 has resulted in a slight improvement inthe selectivity for the second-generation PDE4 inhibitors such ascilomilast and roflumilast. However, even these compounds are notprovided with a good selectivity towards LPDE4.

Compounds with selective LPDE4 inhibition activity are disclosed inWO2009/018909 (PCT/EP2008/005843).

1-phenyl-2-pyridinyl alkylen alcohols and their use as PDE4 inhibitorsare also described in WO 2008/006509.

However, there remains a need for compounds with improved selectiveLPDE4 inhibition activity.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present invention to provide novelcompounds with selective LPDE4 inhibition activity.

It is another object of the present invention to provide novel methodsof preparing such a compound.

It is another object of the present invention to provide novelintermediates useful in the preparation of such a compound.

It is another object of the present invention to provide novelpharmaceutical compositions which contain such a compound.

It is another object of the present invention to provide novel methodsof treating and/or preventing certain diseases and conditions byadministering such a compound.

It is another object of the present invention to provide novel methodsof preventing and/or treating allergic rhinitis.

It is another object of the present invention to provide novel methodsof preventing and/or treating of atopic dermatitis.

These and other objects, which will become apparent during the followingdetailed description, have been achieved by the inventors' discoverythat compounds of formula (I) as (−) enantiomers act as inhibitors ofthe phosphodiesterase 4 (PDE4) enzyme:

wherein:n is 0 or 1;R1 and R2 may be the same or different, and are independently selectedfrom the group consisting of:

linear or branched C₁-C₆ alkyl, optionally substituted by one or morehalogen atoms;

—OR3 wherein R3 is a linear or branched C₁-C₆ alkyl optionallysubstituted with one or more halogen atoms or C₃-C₇ cycloalkyl groups;and

-   -   —NHSO₂R4 wherein R4 is a linear or branched C₁-C₄ alkyl        optionally substituted with one or more halogen atoms,        wherein at least one of R1 and R2 is —NHSO₂R4.

The invention also encompasses the pharmaceutically acceptable hydrates,solvates, addition complexes, inorganic or organic salts thereof, e.g.sodium, potassium and lysine salts.

The present invention also provides a process for the preparation of thecompounds of formula (I) as reported in Scheme 1 (below), whichcomprises reacting aldehyde (1) with methyldichloropyridine (2) toobtain racemic alcohol (3). This latter is then condensed with a chiralacid such as (S)-naproxen or (S)-acetylmandelic acid to obtain adiastereomeric mixture (10) or (5), respectively, as per routes 1 or 2of scheme 1. Separation into the single diastereoisomers respectively(11) and (13) or (6) and (8) is carried out by chromatography,crystallization or other well known methods, giving after cleavage,respectively enantiomeric alcohols (−) (12) and (+) (14) or (+) (7) and(−) (9). Finally, by reaction with a suitable benzoic acid (15),enantiomers (+) (14) or (+) (7) give compounds of general formula (I).

The present invention also provides a process for the preparation ofcompounds of formula (I) wherein n is 0 as reported in Scheme 1 (below),which comprises the reaction of any enantiomeric alcohol, for instance(+) (14), with a benzoic acid (15).

The present invention also provides a process for the preparation ofcompounds of formula (I) wherein n is 1 as reported in Scheme 1 (below),which comprises the oxidization of enantiomeric alcohol (+) (14) bymeans of an oxidizing agent such as 3-chloroperbenzoic acid, peraceticacid or hydrogen peroxide to obtain the alcohol (+) enantiomer (7),which by reaction with a benzoic acid of formula (15) gives compounds offormula (I) wherein n is 1.

The present invention also provides a process for the preparation ofcompounds of formula (I) wherein n is 1 as reported in Scheme 1 below),which comprises the oxidization of esters of formula (I) wherein n is 0by means of an oxidizing agent such as 3-chloroperbenzoic acid,peracetic acid or hydrogen peroxide.

The present invention also provides intermediate compounds of generalformula (II)

wherein n is as defined above and the carbon atom represented with anasterisk has the (S) configuration.

The present invention also provides pharmaceutical compositionscomprising a compound of formula (I) and one or more pharmaceuticallyacceptable carriers and/or excipients.

The present invention in particular provides pharmaceutical preparationssuitable for administration by inhalation.

The present invention also provides combinations of a compound offormula (I) with a second component selected from the classes oflong-acting β₂ agonists, M3 antagonists and corticosteroids.

The present invention also provides combinations of a compound offormula (I) with a long-acting β₂ agonist selected from the groupconsisting of carmoterol, GSK-642444, indacaterol, mil veterol,arformoterol, formoterol, salbutamol, formoterol, levalbuterol,terbutaline, AZD-3199, BI-1744-CL, LAS-100977, bambuterol,isoproterenol, procaterol, clenbuterol, reproterol, fenoterol, andASF-1020.

The present invention also provides combinations of a compound offormula (I) with a M3 antagonist selected from the group consisting ofaclidinium, tiotropium, ipratropium and oxitropium.

The present invention also provides combinations of a compound offormula (I) with a corticosteroid selected from the group consisting ofdexamethasone, fluticasone, fluticasone furoate, prednisolone,betamethasone, budesonide, mometasone, mometasone furoate, triamcinoloneacetonide, ciclesonide, TPI-1020, beclomethasone, beclomethasonedipropionate, prednisone, deflazacort, hydrocortisone, QAE-397, andflunisolide.

In a preferred embodiment, the present invention provides combinationsof a compound of formula (I) with formoterol or carmoterol.

The present invention also provides compounds of formula (I) for use asa medicament.

Also provided is the use of the compounds of formula (I) in thepreparation of a medicament for the prevention or treatment of anydisease wherein the activity of PDE4 receptors is implicated andinhibition of PDE4 receptor activity is desired.

The present invention also provides a method for the prevention ortreatment of any disease wherein the activity of PDE4 receptors isimplicated and inhibition of PDE4 receptor activity is desired, whichmethods comprises administering to a patient in need thereof atherapeutically effective amount of a compound of formula (I).

The above uses or methods comprise a compound of formula (I) eitheralone or combined with other active ingredients among those formerlyreported.

The above diseases wherein the activity of PDE4 receptors and inhibitionof PDE4 receptors are implicated, comprise diseases of the respiratorytract, characterized by airway obstruction such as astma and COPD.

The present invention also provides methods of preventing and/ortreating allergic rhinitis.

The present invention also provides methods of preventing and/ortreating of atopic dermatitis.

Furthermore, the invention also provides the use of the compounds offormula (I) for the in vitro inhibition of PDE4.

The invention also provides devices which may be a single- or multi-dosedry powder inhaler, a metered dose inhaler or a soft mist nebulizercomprising a compound of formula (I).

The invention also provides kits comprising the pharmaceuticalcompositions of compounds of formula (I), alone or in combination withan additional pharmaceutical ingredient, in admixture with one or morepharmaceutically acceptable carriers and/or excipients, and a devicewhich may be a single- or multi-dose dry powder inhaler, a metered doseinhaler or a soft mist nebulizer.

The present invention provides a set of potent novel PDE4 inhibitorshaving excellent LPDE4 selectivity.

Surprisingly, it has been found that the presence of sulphonamidosubstituents on the benzoate residue markedly improves the potency.

Moreover, it has been surprisingly found that the sulphonylamidoderivatives of the invention, which are (−) enantiomers (see, the carbonatom marked with an asterisk) are more potent than the corresponding (+)enantiomers and racemates.

It has now been found that an unexpectedly beneficial therapeuticeffect, particularly a synergistic effect, is obtained in the treatmentof inflammatory or obstructive diseases of the respiratory tract whenthe compounds of the invention are used in combination with along-acting β₂-agonist.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same become betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a graph which shows the existence of a synergic action for apreferred embodiment of the present invention.

OA=ovoalbumin

Cl=3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester

CARM=carmoterol

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “halogen atoms” as used herein includes fluorine, chlorine,bromine and iodine.

As used herein, the expression “linear or branched C₁-C_(x) alkyl” wherex is an integer greater than 1, such as C₁-C₆ or C₁-C₄ alkyl, refers tostraight or branched chain alkyl groups wherein the number of carbonatoms is in the range 1 to x (e.g. 1 to 6 or 1 to 4). Examples of alkylgroups may thus include methyl, ethyl, n-propyl, isopropyl, t-butyl,pentyl, hexyl and the like.

Optionally in said groups one or more hydrogen atoms can be replaced byhalogen atoms, preferably chlorine or fluorine.

As used herein, the expression “C₃-C₇ cycloalkyl” refers to cyclicnon-aromatic hydrocarbon groups containing 3 to 7 ring carbon atoms.Examples of them may thus include cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl and cycloheptyl.

Unless otherwise provided, when referring to chiral compounds, a degreeof purity “substantially pure” here means at least greater than about97% chirally pure, preferably greater than 99% and most preferablygreater than 99.9%.

The invention is directed to compounds acting as inhibitors of thephosphodiesterase 4 (PDE4) enzyme.

Said compounds inhibit the conversion of cyclic nucleotides, inparticular cyclic adenosine monophosphate (cAMP), into their inactive5′-mononucleotide forms.

In the airways, the physiological responses to elevated intracellularlevels of cyclic nucleotides, in particular of cAMP, lead to thesuppression of the activity of immune and pro-inflammatory cells such asmast cells, macrophages, T lymphocytes, eosinophils and neutrophils,resulting in a decrease of the release of inflammatory mediators whichinclude cytokines such as IL-1, IL-3 and tumor necrosis factor-alpha(TNF-α). It also leads to an airway smooth muscle relaxation and adecrease in oedema.

The catalytic site of PDE4 has been previously identified: it mainlycomprises a hydrophobic region in which two sub-pockets are present,e.g. S_(o) and S₁, and a hydrophilic region containing the metal ionsZn²⁺ and Mg²⁺, that in turn comprises the sub-pocket S₂ spreading aroundthe metal ions and a sub-pocket S₃ which branches approximately 90° fromthe middle of the hydrophobic pocket.

Most of the known compounds are provided with a moiety capable ofinteracting with the sub-pockets S₀ and S₁ of the hydrophobic regionsuch as a substituted cathecol group and with another moiety able ofindirectly interacting with the metal ions of the S₂ sub-pocket, forexample a heterocycle such as pyridine or pyrrolidone.

The present invention is directed to compounds that can maintain theinteractions with the sub-pockets S₀ and S₁ by means of the substitutedcatechol moiety and the interaction with the metal ions region by meansof the pyridine ring like other known PDE4 inhibitors, but differingfrom them, for the presence of a sulfonylamino-benzoic acid group, whichenable them to establish an additional interaction with the sub-pocketS₃.

In particular the present invention relates to compounds of formula (I)as defined earlier, including the pharmaceutically acceptable inorganicand organic salts, hydrates, solvates or addition complexes thereof.

Preferred groups of compounds of formula (I) are those wherein:

R1 is —NHSO₂R4, R2 is —OR3, and n is 0;

R1 is —NHSO₂R4, R2 is —OR3, and n is 1;

R1 is —NHSO₂R4, wherein R4 is methyl, R2 is —OR3, wherein R3 iscyclopropylmethyl, and n is 0;

R1 is —NHSO₂R4, wherein R4 is methyl, R2 is —OR3, wherein R3 iscyclopropylmethyl, and n is 1;

R1 is linear or branched C₁-C₆ alkyl, R2 is —NHSO₂R4, and n is 0;

R1 is methyl, R2 is —NHSO₂R4, wherein R4 is methyl, and n is 0;

R1 is linear or branched C₁-C₆ alkyl, R2 is —NHSO₂R4, and n is 1;

R1 is methyl, R2 is —HNSO₂R4, wherein R4 is methyl, and n is 1;

R2 is linear or branched C₁-C₆ alkyl, R1 is —NHSO₂R4, and n is 0;

R2 is methyl, R1 is —HNSO₂R4, wherein R4 is methyl, and n is 0;

R2 is linear or branched C₁-C₆ alkyl, R1 is —NHSO₂R4, and n is 1;

R2 is methyl, R1 is —NHSO₂R4, wherein R4 is methyl, and n is 1;

R1 is —OR3, R2 is —NHSO₂R4, and n is 0;

R1 is —OR3, R2 is —NHSO₂R4, and n is 1;

R1 is —OR3 wherein R3 is cyclopropylmethyl, R2 is —NHSO₂R4 and R4 ismethyl, and n is 1;

R1 is —OR3, R2 is —NHSO₂R4, and n is 1;

both R1 and R2 are —NHSO₂R4, and n is 0;

both R1 and R2 are —NHSO₂R4, wherein R4 is methyl, and n is 0;

both R1 and R2 are —NHSO₂R4, and n is 1; and

both R1 and R2 are —NHSO₂R4, wherein R4 is methyl, and n is 1.

It will be apparent to those skilled in the art that compounds offormula (I) contain at least one asymmetric center, presentlyrepresented by the carbon atom with an asterisk, and therefore exist asoptical stereoisomers.

The present invention is directed to the compounds of formula (I) whichare (−) enantiomers with configuration (S) at the carbon atomrepresented with an asterisk.

The present invention is also directed to the intermediate compounds offormula (II) wherein the carbon atom represented with an asterisk hasthe (S) configuration.

The compounds of formula (I) show an in vitro inhibitory activity towardthe PDE4 enzyme in the nM range, and they are endowed with a remarkableactivity in the lungs upon intra-tracheal administration in an animalmodel of COPD.

They may also exhibit sustained pulmonary levels in the lungs, beingundetectable in plasma, which is an index of a short systemic action.

According to preferred embodiments, the present invention provides thecompounds of formula (I) reported below:

Compound Chemical name C1(−)-3-Cyclopropylmethoxy-4-methanesulfonylamino- benzoic acid1-(3-cyclopropylmethoxy-4- difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethyl ester C2(−)-3-Cyclopropylmethoxy-4-methanesulfonylamino- benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C3(−)-4-Cyclopropylmethoxy-3-methanesulfonylamino- benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin- 4-yl)-ethyl esterC4 (−)-3,4-Bis-methanesulfonylamino-benzoic acid 1-(3-cyclopropyl-methoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C5(−)-3-Methanesulfonylamino-4-methyl-benzoic acid 1-(3-cyclopropyl-methoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C6(−)-4-Methanesulfonylamino-3-methyl-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester

The above compounds have been conveniently identified as (−) enantiomerswhich, however, have (S) configuration at the carbon atom marked with anasterisk. As such, these same compounds can be also identified as perthe following table:

Compound Chemical name C13-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(S)-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethyl ester C23-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(S)-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C34-Cyclopropylmethoxy-3-methanesulfonylamino-benzoic acid1-(S)-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C43,4-Bis-methanesulfonylamino-benzoic acid 1-(S)-(3-cyclopropyl-methoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C53-Methanesulfonylamino-4-methyl-benzoic acid 1-(S)-(3-cyclopropyl-methoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethyl ester C64-Methanesulfonylamino-3-methyl-benzoic acid1-(S)-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy- pyridin-4-yl)-ethyl ester

Advantageously, the compounds of the invention are characterized byselectivity toward LPDE4 higher than that toward HPDE4, as obtained bythe determination of their IC₅₀ values.

In the case of LPDE4, the IC₅₀ is the molar concentration of the testcompound producing 50% inhibition of cAMP disappearance, assessed asdescribed in Cortijo J et al., Br. J. Pharmacol., 1993, 108: 562-568,which is incorporated herein by reference in its entirety. In the caseof HPDE4 instead, the IC₅₀ is the molar concentration of the testcompound producing 50% inhibition of the binding of [H³] rolipram,assessed as described in Duplantier A J et al., J. Med. Chem., 1996; 39:120-125, which is also incorporated herein by reference in its entirety.

Preferably, the HPDE4/LPDE4 IC₅₀ ratio for the compounds of theinvention is higher than 5, more preferably higher than 10, even morepreferably higher than 20 and most preferably higher than 100.

The compounds of formula (I) may be prepared conventionally according toknown methods. Some of the processes which can be used are describedbelow and reported in Scheme 1.

Procedure for the Preparation of Compounds of Formula (I)

According to a particular embodiment of the present invention, thecompounds of formula (I) may be prepared, for example, following thesynthetic pathways described in Scheme 1.

Racemic alcohol (3) may be prepared by reacting aldehyde (1) withmethyldichloropyridine (2).

Route 1.

Racemic alcohol (3) may be separated into (−) (12) and (+) (14)enantiomers by known methods, such as by reacting the racemic mixturewith a suitable chiral auxiliary thus obtaining a mixture ofdiastereoisomers. Such diastereoisomers may be separated bycrystallization or by chromatography or by means of enzymes according toknown methods. Subsequently, the chiral auxiliary may be removed fromdiastereoisomers to give the desired chiral alcohol as a singleenantiomer. Alternatively, the alcohol racemic mixture may be resolvedby means of chromatography with a chiral stationary phase, according toknown methods (see, “Enantiomer Separation: Fundamentals and PracticalMethods” F. Toda, Springer-Verlag 2004; and “Drug Stereochemistry:Analytical Methods and Pharmacology”, Irving W. Wainer, CRC Press, 1993,which are both incorporated herein by reference in their entireties).

In particular, racemic alcohol (3) may be condensed with a chiral acidsuch as (S)-naproxen and the obtained diastereomeric mixture (10) may beseparated into the two single diastereoisomers (11) and (13) bychromatography. After cleavage of the single diastereomeric esters byhydrolysis in an aqueous solvent or by alcoholysis in an alcoholicsolvent, using acidic or basic conditions, enantiomeric pure alcoholintermediates (−) (12) and (+) (14) may be obtained.

Route 2.

Racemate (4), obtained by oxidation of racemate (3) carried outaccording to conventional methods, may be reacted with a chiral acidsuch as (S)-acetylmandelic acid so obtaining a mixture of twodiastereoisomers (5). By trituration with diethyl ether andcrystallization in a solvent such as isopropanol, ethanol or methanol,or by chromatographic separation, single diastereomeric esters (6) and(8) may be obtained.

After cleavage of single diastereomeric esters by hydrolysis in anaqueous solvent or by alcoholysis in an alcoholic solvent, using acidicor basic conditions, enantiomeric pure alcohol intermediates (+) (7) and(−) (9) may be obtained.

Compounds of formula (I) wherein n is 0 may be prepared by reacting theproper enantiomeric alcohol (+)(14) with benzoic acid (15) in thepresence of a suitable strong base such as lithium diisopropylamide(LDA), NaH, or dimethylaminopyridinc (DMAP) and in the presence of acondensing agent such as 1-Ethyl-3-[3-dimethylaminopropyl]-carbodiimidehydrochloride (EDC) or N-hydroxybenzotriazole (HOBT) in a solvent suchas dichloromethane. Other solvents may be used, such asdimethylformamide (DMF), tetrahydrofuran (THF), chloroform, dioxane orany other aprotic solvent known to those skilled in the art. In aparticular embodiment, the reaction may also be carried out in theabsence of solvents.

Compounds of formula (I) wherein n is 1 may be prepared by oxidizingcorresponding compounds of formula (I) wherein n is 0 by means of anoxidizing agent such as 3-chloroperbenzoic acid, peracetic acid orhydrogen peroxide in solvents such as chloroform, dichloromethane oracetic acid (route B).

Alternatively, compounds of formula (I) wherein n is 1 may also beprepared by first oxidizing alcohol enantiomers (+) (14), by means ofthe aforementioned operative conditions, thus obtaining alcoholenantiomers (+) (7). Subsequent reaction between the given alcoholenantiomer with a benzoic acid of formula (15), thus provides the abovecompounds of formula (I) wherein n is 0 (route A).

Separation of (+) (7) and (−) (9) enantiomers from racemic alcohol (4),which in its turn be obtained by oxidation of racemic alcohol (3), maybe carried out by known methods, as described above for separation ofenantiomers of racemic alcohol (3).

The skilled person should be aware that optional variations to thesynthetic steps reported in scheme 1 may be applied as well to thepreparation of the compounds of the invention.

In particular, the order of reactions may be performed so as to get thedesired compounds or intermediates thereof, as well as to the choice ofoperative conditions being adapted, including solvents, optionaloxidizing agents, condensing agents, and the like.

As an example, in case chemically reactive substituents are present inany of the starting materials or intermediates thereof, that might giverise to unwanted side reactions, suitable protection of those samesubstituents may be carried out before the reaction takes place.

By analogy, subsequent deprotection may be then carried out, so as toobtain again the above chemically reactive substituent or group in thefree form.

The protection and deprotection of functional groups is described in“Protective Groups in Organic Chemistry,” 3rd edition, T. W. Greene andP. G. M. Wuts, Wiley-Interscience (1999) and in “Protecting Groups,” P.J. Kocienski, Georg Thieme Verlag (1994) both of which are incorporatedherein by reference in their entireties.

According to the present process for the preparation of the compounds ofthe invention, and variants thereof, the starting materials of formula(1) and (2) as well as any additional reactant [(e.g. of formula (15)],auxiliar of chirality, solvent or agent being employed, is known or maybe easily prepared according to known methods.

The present invention also provides pharmaceutical compositions ofcompounds of formula (I) in admixture with one or more pharmaceuticallyacceptable carriers, for example those described in Remington'sPharmaceutical Sciences Handbook, XVII Ed., Mack Pub., N.Y., U.S.A,which is incorporated herein by reference in its entirety.

Examples include diluents (such as sucrose, mannitol, lactose, starches)and known excipients, including suspending agents, solubilizers,buffering agents, binders, disintegrants, preservatives, colorants,flavours, lubricants and the like. Time release capsules, tablets andgels are also advantageous in administering the compounds of the presentinvention.

Administration of the compounds of the present invention may beaccomplished according to patient needs, for example, orally, nasally,parenterally, e.g. subcutaneously, intravenously, intramuscularly,intrasternally and by infusion, by inhalation, rectally, vaginally,topically, locally, transdermally, and by ocular administration. Varioussolid oral dosage forms may be used for administering compounds of theinvention including such solid forms as tablets, gelcaps, capsules,caplets, granules, lozenges and bulk powders.

Various liquid oral dosage forms may also be used for administeringcompounds of the invention, including aqueous and non-aqueous solutions,emulsions, suspensions, syrups, and elixirs. Such dosage forms can alsocontain known suitable inert diluents such as water and known suitableexcipients such as preservatives, wetting agents, sweeteners, flavours,as well as agents for emulsifying and/or suspending the compounds of theinvention. The compounds of the invention may be injected, for example,intravenously, in the form of an isotonic sterile solution. Otherpreparations conventionally known in the art are also possible.

Suppositories for rectal administration of the said compounds of theinvention may be prepared by mixing the compound with a suitableexcipient such as cocoa butter, salicylates and polyethylene glycols.

Formulations for vaginal administration may be in the form of cream,gel, paste, foam, or spray formula containing, in addition to the activeingredient, conventional carriers.

For topical administration, the pharmaceutical compositions may be inthe form of creams, ointments, liniments, lotions, emulsions,suspensions, gels, solutions, pastes, powders, sprays, and dropssuitable for administration to the skin, eye, ear or nose. Topicaladministration may also involve transdermal administration, e.g. bymeans of transdermal patches.

For the treatment of the diseases of the respiratory tract, thecompounds of the invention are preferably administered by inhalation.

Inhalable preparations include inhalable powders, propellant-containingmetering aerosols or propellant-free inhalable formulations.

For administration as a dry powder, single- or multi-dose inhalers knownfrom the prior art may be utilized. In that case, the powder may befilled in gelatine, plastic or other capsules, cartridges or blisterpacks or in a reservoir.

A diluent or carrier, generally chemically inert to the compounds of theinvention, e.g. lactose or any other additive suitable for improving therespirable fraction may be added to the powdered compounds of theinvention.

Inhalation aerosols containing propellant gas such as hydrofluoroalkanesmay contain the compounds of the invention either in solution or indispersed form. The propellant-driven formulations may also containother ingredients such as co-solvents, stabilizers and optionally otherexcipients.

The propellant-free inhalable formulations comprising the compounds ofthe invention may be in form of solutions or suspensions in an aqueous,alcoholic or hydroalcoholic medium and they may be delivered by jet orultrasonic nebulizers known from the prior art or by soft-mistnebulizers such as Respimat®.

The compounds of the invention may be administered as the sole activeagent or in combination with one or more other pharmaceutical activeingredients including those currently used in the treatment ofrespiratory disorders, e.g. β₂-agonists, corticosteroids and M3antagonists.

The dosages of the compounds of the invention may depend upon a varietyof factors including the particular disease to be treated, the severityof the symptoms, the route of administration, the frequency of thedosage interval, the particular compound utilized, the efficacy,toxicology profile, and pharmacokinetic profile of the compound.

Advantageously, the compounds of formula (I) may be administered forexample, at a dosage comprised between 0.001 and 1000 mg/day, preferablybetween 0.1 and 500 mg/day.

When they are administered by inhalation route, the dosage of thecompounds of formula (I) is advantageously comprised between 0.01 and 20mg/day, preferably between 0.1 and 10 mg/day.

Preferably, the compounds of formula (I) alone or combined with otheractive ingredients may be administered for the prevention and/ortreatment of any obstructive respiratory disease such as asthma, chronicbronchitis and chronic obstructive pulmonary disease (COPD).

However the compounds of formula (I) may be administered for theprevention and/or treatment of any disease wherein the activity of PDE4receptors is implicated and inhibition of PDE4 receptor activity isdesired, or a disease state which is mediated by PDE4 activity (forinstance a disease state in which PDE4 is overexpressed or overactive).Examples of such diseases include: allergic disease states such asatopic dermatitis, urticaria, allergic rhinitis, allergicconjunctivitis, vernal conjunctivitis, eosinophilic granuloma,psoriasis, inflammatory arthritis, rheumatoid arthritis, septic shock,ulcerative colitis, Crohn's disease, reperfusion injury of themyocardium and brain, chronic glomerulonephritis, endotoxic shock,cystic fibrosis, arterial restenosis, artherosclerosis, keratosis,rheumatoid spondylitis, osteoarthritis, pyresis, diabetes mellitus,pneumoconiosis, toxic and allergic contact eczema, atopic eczema,seborrheic eczema, lichen simplex, sunburn, itching in the anogenitalarea, alopecia areata, hypertrophic scars, discoid lupus erythematosus,systemic lupus erythematosus, follicular and wide-area pyodermias,endogenous and exogenous acne, acne rosacea, Beghet's disease,anaphylactoid purpura nephritis, inflammatory bowel disease, leukemia,multiple sclerosis, gastrointestinal diseases, autoimmune diseases, andthe like.

They also include neurological and psychiatric disorders such asAlzheimer's disease, multiple sclerosis, amylolaterosclerosis (ALS),multiple systems atrophy (MSA), schizophrenia, Parkinson's disease,Huntington's disease, Pick's disease, depression, stroke, and spinalcord injury.

Other features of the invention will become apparent in the course ofthe following descriptions of exemplary embodiments which are given forillustration of the invention and are not intended to be limitingthereof.

EXAMPLES Example 1 Preparation of1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethanol(3)

A solution of 3-cyclopropylmethoxy-4-difluoromethoxy-benzaldehyde (5.00g) and 3,5-dichloro-4-methylpyridine (2.57 g) in 50 ml dry THF wascooled to −30° C. Solid potassium t-butoxide (tBuOK, 1.96 g) was addedportionwise maintaining the temperature between −30° C. and −20° C.,thus obtaining a dark red solution. After completion of the addition,the mixture was stirred at −30° C. for 1 hour. A saturated aqueoussolution of NH₄Cl (50 ml) was then added to the reaction mixture,maintaining the temperature between −5° C. and −10° C. The color of thereaction mixture turned to yellow.

The mixture was then extracted with EtOAc. The organic layer was driedover Na₂SO₄ and the solvent was removed by evaporation. The residue wastreated with 30 ml of a mixture of petroleum ether/EtOAc=8/2; theprecipitate was filtered and dried, obtaining 4.83 g of the titlecompound that was employed in the next step without furtherpurification.

MS/ESI⁺ 404-406 [MH]⁺.

Example 2 Preparation of1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethanol(4)

Compound (3) (13.0 g) was dissolved in CH₂Cl₂ (250 ml) then m-chloroperbenzoic acid (16.5 g) was added, and the resulting solution wasstirred at room temperature for 2 hours. Na₂S₂O₃ (25.4 g) was added, andthe mixture was vigorously stirred at r.t. for 1 hour. The solid residuewas filtered off, the solution was washed with 1N NaOH (3×100 ml) thenthe organic phase was dried over Na₂SO₄ and the solvent was removed byevaporation to give 10.3 g of the desired product (4) as a white solidthat was used in the next steps without further purification.

MS/ESI⁺ 420-422 [MH]⁺

Example 3 Preparation of Acetoxy-phenyl-acetic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester (5, mixture of diastereoisomers)

Compound (4) (19.95 g), (S)-acetylmandelic acid (9.22 g),1-ethyl-3-[3-dimethylamino propyl]carbodiimide hydrochloride (18 g), and4-dimethylaminopyridine (2.89 g) were dissolved, under N₂ atmosphere, indry CH₂Cl₂ (300 ml). The reaction mixture was stirred at roomtemperature overnight. A 5% aqueous solution of NaHCO₃ (200 ml) wasadded and the aqueous phase was extracted with CH₂Cl₂ (3×100 ml). Thecombined organic phases were dried over Na₂SO₄ and the solvent wasevaporated under reduced pressure to give the title compound (5) asmixture of two diastereoisomers (32 g); separation of the twodiastereoisomers is described in Examples 4 and 6.

Example 4 Preparation of (+)-Acetoxy-phenyl-acetic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester (6)

The crude diastereomeric mixture (5) (32 g) was triturated with Et₂O(100 ml), sonicated and filtered. The procedure was repeated four timesin order to obtain a solid mixture enriched in diastereoisomer (6). Thissolid was crystallized from iPrOH (80 ml) and filtered to give 9.65 g ofcompound (6) with diastereomeric purity>95%. The diastereomeric puritywas determined by HPLC analysis and by analytical chiral HPLC performedon Chiracel OD column (isocratic elution with hexane:isopropanol 40:60,flow 0.45 ml/min, retention time=27.2 min).

MS/ESI⁺ 596, 598 [MH]

1H NMR (300 MHz, DMSO-d6) ppm 8.57 (s, 2H), 7.27-7.44 (m, 5H), 6.91-7.18(m, 1H), 7.03 (t, 1H), 6.71-6.79 (m, 2H), 5.95 (dd, 1H), 5.85 (s, 1H),3.72 (dd, 1H), 3.60 (dd, 1H), 3.41 (dd, 1H), 3.23 (dd, 1H), 2.13 (s,3H), 1.07-1.31 (m, 1H), 0.48-0.72 (m, 2H), 0.21-0.44 (m, 2H)

[α]_(D)=+14° (c=0.54, MeOH)

Example 5 Preparation of(+)-1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethanol(7)

Compound (6) (6.42 g) was suspended in methanol (350 ml) then asaturated solution of NaHCO₃ (175 ml) was added. The white suspensionwas vigorously stirred at room temperature overnight. The reactionmixture was diluted with CH₂Cl₂ (700 ml) and washed with a 5% aqueoussolution of NaHCO₃ (300 ml); the aqueous phase was extracted with CH₂Cl₂(2×300 ml), the combined organic layers were dried over Na₂SO₄, and thesolvent was removed by evaporation under vacuum. The crude white solidobtained was triturated with Et₂O (2×100 ml) and filtered to give 3.88 gof compound (7) with enantiomeric purity>99%. The enantiomeric puritywas determined by analytical chiral HPLC performed on Chiraccl OD column(isocratic elution with hexane:isopropanol 30:70, flow 0.35 ml/min,retention time=22.3 min).

MS/ESI⁺ 420-422 [MH]⁺

¹H NMR (300 MHz, DMSO-d6) ppm 8.51 (s, 2H), 7.11 (d, 1H), 7.05 (d, 1H),6.88 (dd, 1H), 7.01 (t, 1H), 5.59 (d, 1H), 4.84 (dd, 1H), 3.89 (dd, 1H),3.84 (dd, 1H), 3.18 (dd, 1H), 3.02 (dd, 1H), 1.03-1.35 (m, 1H),0.46-0.67 (m, 2H), 0.24-0.46 (m, 2H)

[α]_(D)=+68° (c=0.5, MeOH)

Example 6 Preparation of (+)-Acetoxy-phenyl-acetic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester (8)

The crude diastereomeric mixture (5) was triturated with Et₂O (100 ml),sonicated and filtered. The procedure was repeated four times, and thefiltrates were collected and evaporated under reduced pressure to give asolid mixture enriched in diastereoisomer (8) that was crystallized fromiPrOH (100 ml) to give 6.4 g of compound (8) as a white solid withdiastereomeric purity>99%. The diastereomeric purity was determined byHPLC analysis and by analytical chiral HPLC performed on Chiracel ODcolumn (isocratic elution with hexane:isopropanol 40:60, flow 0.45ml/min, retention time=21.6 min).

MS/ESI⁺ 596, 598 [MH]⁺

¹H NMR (300 MHz, DMSO-d6) ppm 8.27 (s, 2H), 7.27-7.45 (m, 5H), 7.20 (d,1H), 7.08 (d, 1H), 7.00 (dd, 1H), 7.08 (t, 1H), 5.97 (dd, 1H), 5.85 (s,1H), 3.93 (dd, 1H), 3.89 (dd, 1H), 3.33 (dd, 1H), 3.17 (dd, 1H), 2.07(s, 3H), 1.14-1.38 (m, 1H), 0.50-0.71 (m, 2H), 0.21-0.47 (m, 2H)

[α]_(D)=+26° (c=0.55, MeOH)

Example 7 Preparation of(−)-1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethanol(9)

Compound (8) (1.18 g) was suspended in methanol (50 ml) then a saturatedsolution of NaHCO₃ (25 ml) was added. The white suspension wasvigorously stirred at room temperature for 24 hours. The reactionmixture was diluted with CH₂Cl₂ (700 ml) then a 5% aqueous solution ofNaHCO₃ (300 ml) was added, and the phases were separated. The aqueousphase was extracted with CH₂Cl₂ (2×100 ml), the combined organic layerswere dried over Na₂SO₄, and the solvent was removed by evaporation undervacuum. The crude white solid obtained was triturated twice with Et₂O(50 ml) and once with CH₂Cl₂ (20 ml), then was filtered to give 0.74 gof compound (7) with enantiomeric purity>99%. The enantiomeric puritywas determined by analytical chiral HPLC performed on Chiracel OD column(isocratic elution with hexane:isopropanol 30:70, flow 0.35 ml/min,retention time=24.0 min).

MS/ESI⁺ ⁴²⁰-422 [MH]⁺

¹H NMR (300 MHz, DMSO-d6) ppm 8.51 (s, 2H), 7.11 (d, 1H), 7.05 (d, 1H),6.88 (dd, 1H), 7.01 (t, 1H), 5.59 (d, 1H), 4.84 (dt, 1H), 3.89 (dd, 1H),3.84 (dd, 1H), 3.18 (dd, 1H), 3.02 (dd, 1H), 1.08-1.32 (m, 1H),0.47-0.66 (m, 2H), 0.26-0.45 (m, 2H)

[α]_(D)=−61° (c=0.5, MeOH)

Example 8 2-(6-Methoxy-naphthalen-2-yl)-propionic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester (10, mixture of diastereoisomers 11 and 13)

Compound (3) (12.0 g) was dissolved in DMF (100 ml) then(S)-2-(6-methoxy-naphthalen-2-yl)-propionic acid (7.5 g),4-dimethylaminopyridine (3.6 g), and1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (5.7 g) wasadded. After stirring at rt for 4 hours, water (1000 ml) is added. Themixture was extracted with EtOAc (500 ml×2), the combined organic layersare dried over sodium sulphate, and the solvent was removed byevaporation under reduced pressure to afford 17.0 g of an oil which iscrystallized from EtOH thus obtaining 11.5 g of the title compound asmixture of diastereomers (11) and (13),

¹H NMR (200 MHz, CDCl₃) ppm 8.43 and 8.60 (2s, 1H each, 2H), 7.51-7.68(m, 3H), 7.10-7.23 (m, 3H), 6.85-6.97 (m, 2H), 6.51-6.68 (m, 1H),6.22-6.97 (t, 1H, CHF₂), 6.00-6.13 (m, 1H), 3.93-3.95 (s, 3H, OCH₃),3.72-3.84 (m, 2H), 3.07-3.57 (m, 3H), 1.42-1.45 (d, 3H, CH₃), 0.94-1.25(m, 1H), 0.51-0.67 (m, 2H), 0.12-0.36 (m, 2H).

MS/ESI⁺ 616, 618 [MH]⁺

Example 9 (+)-2-(6-Methoxy-naphthalen-2-yl)-propionic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester (second eluted diastereoisomer) (13)

The compound was isolated from the diastereomeric mixture of example 8by HPLC separation using a Daisogel 10 μm, 50×300 mm column; eluent:n-hexane/methyl-tert-butyl-ether/isopropyl alcohol: 90/9.9/0.1; flow: 80ml/min.; loading: 300 mg per injection; elution time: from 11 to 20 min.The collected fractions were evaporated and the residue was crystallizedfrom n-hexane/isopropyl-alcohol.

¹H NMR (200 MHz, CDCl₃) ppm 8.60 (s, 2H), 7.68-7.75 (m, 2H), 7.58-7.59(m, 1H), 7.27-7.29 (d, 1H), 7.12-7.24 (m, 2H), 6.98-7.04 (m, 1H),6.73-6.78 (dd, 1H), 6.67-6.68 (d, 1H), 6.60-7.35 (t, 1H, CHF₂),5.99-6.06 (m, 1H), 3.84-3.87 (m, 4H), 3.47-3.55 (m, 2H), 3.32-3.41 (dd,1H), 3.22-3.29 (m, 1H), 1.33-1.37 (d, 3H, CH₃), 0.96-1.03 (m, 1H),0.43-0.52 (m, 2H), 0.13-0.21 (m, 2H).

MS/ESI⁺ 616, 618 [MH]⁺

[α]_(D)=+52.8° (c=0.5, MeOH)

Example 10 (+)-2-(6-Methoxy-naphthalen-2-yl)-propionic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester (first eluted diastereoisomer) (11)

The compound was isolated from the diastereomeric mixture of example 8by HPLC separation using a Daisogel 10 μm, 50×300 mm column; eluent:n-exane/methyl-tert-butyl-ether/isopropyl-alcohol: 90/9.9/0.1; flow: 80ml/min.; loading: 300 mg per injection; elution time: from 7 to 10 min.The collected fractions were evaporated and the residue was crystallizedfrom n-hexane/isopropyl-alcohol.

¹H NMR (200 MHz, CDCl₃) ppm 8.27 (s, 2H), 7.64-7.80 (m, 2H), 7.56-7.57(m, 1H), 7.28-7.29 (d, 1H), 7.14-7.20 (m, 3H), 6.68-7.42 (t, 1H, CHF₂),6.93-6.98 (m, 2H), 6.00-6.07 (m, 1H), 3.88-3.92 (m, 4H), 3.71-3.84 (m,2H), 3.39-3.51 (dd, 1H), 3.16-3.25 (dd, 1H), 1.33-1.37 (d, 3H, CH₃),1.08-1.23 (m, 1H), 0.50-0.59 (m, 2H), 0.34-0.26 (m, 2H).

MS/ESI⁺ 616, 618 [MH]⁺

[α]_(D)=+45° (c=0.5, MeOH)

Example 11(+)-1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethanol(14)

To a suspension of (+)-2-(6-methoxy-naphthalen-2-yl)-propionicacid-1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester (13) (14.0 g) in methanol (110 ml), potassium tert-butoxide (5.1g) was added. The resulting mixture was stirred at rt for 2 hours,obtaining a clear solution. Water was slowly added under stirring toincipient precipitation (turbid solution).

After stirring for a further 60 minutes, the precipitated solid wasfiltered, washed with water and dissolved in chloroform (100 ml). Thesolution was dried over sodium sulphate and the solvent removed undervacuum. The residue was crystallized in chloroform/hexane=1/2.5 toobtain 8.1 g of white solid.

¹H NMR (200 MHz, CDCl₃) ppm δ 8.45 (s, 2H), 7.19-7.08 (d, 1H), 7.06-7.00(d, 1H), 6.95-6.85 (dd, 1H), 6.99-6.24 (t, 1H, CHF₂), 5.18-5.00 (m, 1H),3.98-3.78 (m, 2H), 3.54-3.35 (m, 1H), 3.31-3.15 (m, 1H), 2.04-1.94 (d,1H, OH), 1.40-1.14 (m, 1H), 0.75-0.53 (m, 2H), 0.50-0.29 (m, 2H).

MS/ESI⁺404, 406 [MH]⁺.

[α]_(D)=+9.35° (c=1, CHCl₃),

Example 12(−)-1-(3-Cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethanol(12)

Starting from diastereoisomer (11), following the procedure of Example10, alcohol (12) was obtained.

MS/ESI⁺ 404, 406 [MH]⁺.

[α]_(D)=−9.15° (c=1, CHCl₃).

Example 13 Preparation of Alcohol (7) by Oxidation of Alcohol (14)

Compound (14) (3.0 g) was dissolved in CH₂Cl₂ (100 ml). 70% m-Chloroperbenzoic acid (5.4 g) was added, and the resulting solution wasstirred at room temperature for 18 hours. Solid Na₂S₂O₃ (5 g) was thenadded, and the mixture was vigorously stirred at r.t. for 30 minutes.The solid residue was removed by filtration; the organic solution wasdiluted with additional 100 ml of CH₂Cl₂ and washed with aqueoussaturated NaHCO₃ solution (3×100 ml). The organic phase was dried overNa₂SO₄, and the solvent was removed by evaporation. The residue wastriturated in EtOAc (20 ml) to give 1.9 g of the desired product 7 as awhite solid, which was used in the next step without furtherpurification.

¹H NMR (200 MHz, CDCl₃) ppm 8.14 (s, 2H), 7.18-7.09 (d, 1H), 7.07-7.02(d, 1H), 6.92-6.83 (dd, 1H), 7.01-6.22 (t, 1H, CHF₂), 5.10-4.96 (m, 1H),3.96-3.84 (d, 2H), 3.45-3.29 (m, 1H), 3.23-3.07 (m, 1H), 3.24-3.17 (d,1H, OH), 1.41-1.67 (m, 1H), 0.75-0.53 (m, 2H), 0.50-0.29 (m, 2H).

MS/ESI⁺ 420, 422 [MH]⁺

[α]_(D)=+65.0° (c=0.5, MeOH)

Example 14 Preparation of Alcohol (9) by Oxidation of Alcohol (12)

Alcohol (9) may be obtained following the procedure described in Example13, using alcohol (12) in place of alcohol (14) as starting material.

MS/ESI⁺ 420, 422 [MH]⁺

[α]_(D)=−60.6° (c=0.5, MeOH)

Example 15 Preparation of(−)-3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-pyridin-4-yl)-ethylester (C1) Step 1:3-Cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methanesulfonyl)-aminobenzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester

1-Ethyl-3-[3-dimethylamino propyl]carbodiimide hydrochloride (2.85 g)was added to a solution of alcohol (14) (2.0 g), 4-dimethylaminopyridine(0.3 g),3-cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methanesulfonyl)-amino-benzoicacid (2.0 g) in dry CH₂Cl₂ (180 ml) at r.t. under nitrogen atmosphere.

After stirring at r.t. overnight, the mixture was washed with 5% aqueousHCl (2×100 ml); the organic phase was separated and washed with asaturated aqueous solution of NaHCO₃ (2×100 ml), dried over Na₂SO₄ andevaporated to dryness. The crude was purified by flash chromatography onsilica gel in gradient elution (hexane/EtOAc 10/1 to 6/4) to afford 1.4g of the title compound.

Step 2: Preparation of C1

3-Cyclopropylmethoxy-4-(N-tert-butoxycarbony-N-methanesulfonyl)-amino-benzoicacid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester (1.4 g) was dissolved in CH₂Cl₂ (140 ml). A 4M solution of HCl indioxane (40 ml) was added and the resulting mixture was stirred at r.t.for 24 hours. The reaction mixture was then evaporated to dryness, andthe residue was triturated in iPrOH (50 ml) and subsequently in EtOH (50ml) followed by Et₂O (70 ml) to afford 0.880 g of compound (C1).

Analytical characterization of C1 is reported in Table 1.

TABLE 1

Compound A Analytical C1

MS/ESI⁺ 671, 673 [MH]⁺; ¹H NMR (300 MHz, DMSO-d6) ppm 9.13 (br. s., 1 H)8.60 (s, 2 H) 7.55 (dd, 1 H) 7.44-7.49 (m, 1 H) 7.39 (d, 1 H) 7.06 (t, 1H) 6.78-7.33 (m, 3 H) 6.20-6.30 (m, 1 H) 3.87-3.98 (m, 4 H) 3.63-3.78(m, 1 H) 3.38-3.50 (m, 1 H) 3.10 (s, 3 H) 1.09-1.40 (m, 2 H) 0.48-0.67(m, 4 H) 0.28-0.44 (m, 4 H) [α]_(D) = −22° (c = 0.4, MeOH) In thestructure for A, *-indicates the position at which A is attached to therest of the molecule.

Analogously, the following compounds may be prepared:

(−)-4-Cyclopropylmethoxy-3-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester;

(−)-3,4-Bis-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester;

(−)-3-Methanesulfonylamino-4-methyl-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-pyridin-4-yl)-ethylester; and

(−)-4-Methanesulfonylamino-3-methyl-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester.

Example 16 Preparation of(−)-3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester (C2)

Compound (C2) was prepared according to the same synthetic procedure ofExample 15, starting from alcohol intermediate (7). Alternatively,compound (C2) can be prepared starting from compound (C1) as describedin the following Example 17.

Example 17 Preparation of(−)-3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid1-(3-cyclopropylmethoxy-4-difluoromethoxy-phenyl)-2-(3,5-dichloro-1-oxy-pyridin-4-yl)-ethylester (C2) starting from compound (C1)

Compound (C1) (0.69 g) was dissolved in CH₂Cl₂ (20 ml). 70% m-Chloroperbenzoic acid (0.355 g) was added, and the resulting solution wasstirred at room temperature for 18 hours. Solid Na₂S₂O₃ (0.244 g) wasthen added, and the mixture was vigorously stirred at r.t. for 30minutes. The solid residue was removed by filtration; the organicsolution was diluted with additional 20 ml of CH₂Cl₂ and washed withaqueous saturated NaHCO₃ solution (3×20 ml). The organic phase was driedover Na₂SO₄ and the solvent was removed by evaporation. The residue wastriturated in EtOH (20 ml) to give 0.710 g of the desired compound (C2)as a white solid.

The following compounds shown in Table 2 were prepared following thesame route using suitable reagents.

TABLE 2

Compound A Analytical C2

MS/ESI⁺ 687, 689 [MH]⁺; ¹H NMR (300 MHz, DMSO-d6) ppm 9.14 (br. s., 1H), 8.56 (s, 2 H), 7.59 (dd, 1 H), 7.49 (d, 1 H), 7.41 (d, 1 H),7.14-7.27 (m, 2 H), 7.07 (dd, 1 H), 7.06 (t, 1 H), 6.18 (dd, 1 H),3.84-4.04 (m, 4 H), 3.61 (dd, 1 H), 3.34 (dd, 1 H), 3.11 (s, 3 H),1.25-1.43 (m, 1 H), 1.13-1.26 (m, 1 H), 0.49-0.67 (m, 4 H), 0.27-0.47(m, 4 H) [α]_(D) = −47° (c = 0.4, MeOH) C3

¹H NMR (200 MHz, CD₃OD-d4 calibrated at 3.31 ppm) δ ppm 8.42 (s, 2 H),8.13 (d, J = 2.44 Hz, 1 H), 7.85 (dd, J = 8.79, 2.44 Hz, 1 H), 7.12-6.37(t, 1H, CHF₂), 7.00-7.24 (m, 4 H), 6.26-6.40 (m, 1 H), 3.97 (dd, J =14.89, 7.08 Hz, 4 H), 3.75 (dd, J = 13.92, 9.52 Hz, 1 H), 3.45 (dd, J =14.16, 4.39 Hz, 1 H), 2.98 (s, 3 H), 1.17-1.45 (m, 2 H), 0.54-0.75 (m, 4H ), 0.29-0.47 (m, 4 H) [α]_(D) = −36 (c = 0.1, CHCl₃) C4

¹H NMR (200 MHz, CDCl₃ calibrated at 7.26 ppm) δ ppm 8.23 (s, 2 H),7.85-8.01 (m, 2 H), 7.69 (d, J = 8.30 Hz, 1 H), 7.20 (m, 1 H), 7.00-6.25(t, 1H, CHF₂), 6.97-7.11 (m, 2 H), 6.21-6.32 (m, 1 H), 3.91 (d, J = 6.84Hz, 2 H), 3.72 (dd, J = 13.67, 10.74 Hz, 1 H), 3.32 (dd, J = 13.92, 3.66Hz, 1 H), 3.04 (d, J = 17.58 Hz, 6 H), 1.16-1.35 (m, 1 H), 0.55- 0.74(m, 2 H), 0.30-0.45 (m, 2 H) [α]_(D) = −27 (c = 0.1, CHCl₃) C5

¹H NMR (200 MHz, DMSO-d6 calibrated at 2.50 ppm) δ ppm 9.25 (s, 1 H),8.53 (s, 2 H), 7.91 (m, 1 H), 7.76 (d, J = 8.30 Hz, 1 H), 7.43-6.69 (t,1H, CHF₂), 7.40 (d, J = 8.30 Hz, 1 H), 7.19 (d, J = 4.39 Hz, 2 H),7.00-7.12 (m, 1 H), 6.21 (dd, J = 9.52, 4.15 Hz, 1 H), 3.92 (d, J = 6.84Hz, 2 H), 3.63-3.55 (m, 1 H), 3.37 (d, J = 4.39 Hz, 1 H), 2.99 (s, 3 H),2.37 (s, 3 H), 1.11-1.28 (m, 1 H), 0.48-0.65 (m, 2 H), 0.26-0.41 (m, 2H) [α]_(D) = −38.67° C6

¹H NMR (200 MHz, DMSO-d6 calibrated at 2.50 ppm) δ ppm 8.55 (s, 2 H),7.93-7.83 (m, 2 H), 7.49 (d, J = 8.30 Hz, 1 H), 7.43-6.69 (t, 1H, CHF₂),7.03-7.27 (m, 3 H), 6.11- 6.24 (m, 1 H), 3.93 (d, J = 6.84 Hz, 2 H),3.60 (s, 3 H), 2.28 (s, 3 H), 1.11-1.29 (m, 1 H), 0.57 (m, 2 H), 0.34(m, 2 H) [α]_(D) = −58.0° In the structure for A, *-indicates theposition at which A is attached to the rest of the molecule.

The carboxylic acid intermediates employed in the synthesis of thedescribed final compounds are commercially available or are alreadyknown or are synthesized according to known methods.

Example 18 Synthesis of3-Cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methane-sulfonyl)-amino-benzoicacid

Step 1: 3-Hydroxy-4-nitro-benzoic acid methyl ester

3-Hydroxy-4-nitro-benzoic acid (10 g) was dissolved in MeOH (500 ml).96% H₂SO₄ (2 ml) was added, and the mixture was heated to 60° C. for 18hours. The reaction mixture was concentrated to approx. 200 ml, dilutedwith EtOAc (200 ml) and washed with an aqueous saturated solution ofNaHCO₃ (2×20 ml). The organic layer was dried over Na₂SO₄ and thesolvent was removed by evaporation to yield 10.5 g of the desiredintermediate.

Step 2: 3-Cyclopropylmethoxy-4-nitro-benzoic acid methyl ester

3-Hydroxy-4-nitro-benzoic acid methyl ester (10.5 g) was dissolved indry DMF (150 ml) under N₂ atmosphere. K₂CO₃ (24.3 g), KI (2.6 g) andyclopropylmethylbromide (10.3 ml) were added and the mixture was stirredat 50° C. for 6 hours. The reaction mixture was diluted with water (300ml) and extracted with Et₂O (2×200 ml); the combined organic layers weredried over Na₂SO₄ and the solvent was removed by evaporation to yield12.7 g of the desired intermediate.

Step 3: 4-Amino-3-cyclopropylmethoxy-benzoic acid methyl ester

3-Cyclopropylmethoxy-4-nitro-benzoic acid methyl ester (12.7 g) wasdissolved in MeOH (100 ml) and EtOAc (100 ml); 10% Pd/C (1.0 g,suspended in 20 ml of water) was added, and the mixture is hydrogenatedin a Parr apparatus (H₂: 20 psi) for 5 hours. 37% HCl was added (10 ml),and hydrogenation was continued for additional 2 hours to obtaincomplete conversion. The catalyst was filtered over a celite pad, themixture was diluted with EtOAc (200 ml) and washed with an aqueoussaturated solution of NaHCO₃ (2×100 ml). The organic layer was driedover Na₂SO₄ and the solvent was removed by evaporation to yield 10.7 gof the desired intermediate.

Step 4: 3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid methylester

Methyl 3-(cyclopropylmethoxy)-4-aminobenzoate (8.86 g) was dissolved inpyridine (80 mL) at room temperature under N₂ atmosphere.Methanesulfonyl chloride (4.04 mL) was added and the mixture was stirredat r.t. for 18 hours. The reaction mixture was evaporated to dryness,the crude was treated with 1N HCl (500 mL) and extracted with CH₂Cl₂(3×200 mL). The organic layer was dried over Na₂SO₄ and the solvent wasevaporated off to yield 11.7 g of the desired intermediate.

MS/ESI⁺ 300 [MH]⁺

Step 5:3-Cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methanesulfonyl)-amino-benzoicacid methyl ester

3-Cyclopropylmethoxy-4-methanesulfonylamino-benzoic acid methyl ester(3.0 g) was dissolved in CH₂Cl₂ (150 ml). Dimethylaminopyridine (DMAP,1.22 g) and Boc₂O (2.18 g) were added and the mixture was stirred atr.t. for 1 hour. The reaction mixture was washed with 5% aqueous HCl(2×50 ml), the organic layer was dried over Na₂SO₄ and the solvent wasremoved by evaporation. The residue was triturated in Et₂O and filteredto afford 4.0 g of the desired intermediate that was used in the nextsteps without further purification.

Step 6:3-Cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methanesulfonyl)-amino-benzoicacid

Cyclopropylmethoxy-4-(N-tert-butoxycarbonyl-N-methanesulfonyl)-amino-benzoicacid methyl ester (4.0 g) was dissolved in MeOH (100 ml). 1N NaOH (15ml) was added, and the resulting mixture was stirred at r.t. for 1 hour,then was heated to 50° C. for 2 hours. The reaction mixture was thendiluted with EtOAc (250 ml) and washed with 1N HCl (2×100 ml). Theorganic layer was dried over Na₂SO₄ and the solvent was evaporated offto give 3.5 g of the desired acid derivative.

MS/ESI⁺ 386 [MH]⁺.

Legend

*NMR

s=singlet

d=doublet

t=triplet

q=quartet

dd=doublet of doublets

m=multiplet

br=broad

ESI=electrospray

Pharmacological Activity of the Compounds of the Invention

Example 19 In Vitro Determination of PDE4 Inhibitory Activity in thePeripheral Blood Mononuclear Cells (PBMCs) Assay

The assay, which is based on the known inhibitory activity exerted byPDE4 inhibitors on the lipopolyshaccarides (LPS)-induced tumour necrosisfactor-alpha (TNF-α release in peripheral blood mononuclear cells(PBMCs), is performed according to a method previously described(Hatzelmann A et al., J. Pharmacol. Exp. Ther., 2001; 297:267-279; andDraheim R et al., J. Pharmacol. Exp. Ther., 2004; 308:555-563, both ofwhich are incorporated herein by reference in their entireties.

Cryopreserved human PBMCs, (100 μl/well) are incubated in 96-well plates(10⁵ cells/well), for 30 minutes, in the presence or absence (50 microl)of the test compounds whose concentrations range from 10⁻¹² M to 10⁻⁶ M.Subsequently, LPS (3 ng/ml) is added.

After 18 hours incubation at 37° C. in a humidified incubator under anatmosphere of 95% air and 5% CO₂, culture medium is collected and TNF-αis measured by ELISA.

The results regarding compounds C1 to C6, expressed as mean±95%confidence limits of the molar concentration of the test compoundproducing 50% inhibition of LPS-induced TNF-α release (IC₅₀), arecomprised between 0.06 and 4.4 nM. The effects of the tested compoundsare calculated as percentage of inhibition of TNF-α release, assumingLPS-induced TNF-α production in the absence of inhibitor compound as100% and basal TNF-α production of PBMCs in the absence of LPS as 0%.

Example 20 Evaluation of the Ability to Inhibit the Low Affinity LPDE4Versus the Ability to Compete for the High Affinity HPDE4

The affinity toward LPDE4 and HPDE4 is assessed as previously describedrespectively in Cortijo J et al., Br. J. Pharmacol., 1993, 108: 562-568and Duplantier A J et al., J. Med. Chem., 1996; 39: 120-125, both ofwhich are incorporated herein by reference in their entireties.

The concentration of the test compound ranges between 10⁻¹² M and 10⁻⁵M. The values of affinity toward LPDE4 and HPDE4 tested on compounds C1to C6 are comprised between 82 and 477.

In the case of LPDE4, the IC₅₀ is the molar concentration of the testcompound producing 50% inhibition of cAMP disappearance, while in thecase of HPDE4, the IC₅₀ is the molar concentration of the test compoundproducing 50% inhibition of the binding of [H³] rolipram.

The results indicate that the compounds of the invention inhibit LPDE4with subnanomolar affinity and are considerably more selective towardLPDE4 versus HPDE4.

Example 21 Synergistic Activity of Fixed Dose Combination ofCarmoterol/C1 on Carbachol-Induced Contraction in Guinea-Pigs Trachea

Zig-zag tracheal segments are obtained from maleOvoalbumin(OA)-sensitized guinea pigs and two preparations are obtainedfrom a trachea. Each preparation is placed in 20-ml organ bath filledwith oxygenated (O₂ 95% and CO₂ 5%) normal Krebs-Henseleit solution andmaintained at 37° C. Tracheal preparations are connected to isometricforce transducers under a resting tone of 1 g. After an equilibrationperiod of 60 minutes, tracheal preparations are pretreated for 30minutes with C1 (10-7 M), Carmoterol (3*10-10 M), the association C1 andCarmoterol or vehicle, respectively, followed by cumulativeadministration of OA (10⁻¹⁰-10⁻⁵ g/ml). At the end of the OAadministration a maximal concentration of carbachol (10⁻⁵ M) is added toobtain the maximal contraction of each preparation. The effects areexpressed as percent values of the carbachol-induced maximal response(100%).

30-Minute pre-treatment of the preparation with C1 (10⁻⁷ NI) caused aninhibition of the OA-induced contraction of 23%. Similarly theinhibition produced by Carmoterol (3*10-10 M) is 18%.

C1 (10-7 M) and Carmoterol (3*10⁻¹⁰ M)-combination caused a reduction ofthe OA-induced contraction of the 93%.

This study shows that both carmoterol and C1 are potent in antagonizingcarbachol-induced contraction in guinea-pig airways. Moreover, in linewith their complementary molecular mechanism of action, in the frame ofa functional agonism-antagonism, fixed combinations display synergisticeffect in the control of cholinergic contraction in guinea-pigtrachealis

Where a numerical limit or range is stated herein, the endpoints areincluded. Also, all values and subranges within a numerical limit orrange are specifically included as if explicitly written out.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

All patents and other references mentioned above are incorporated infull herein by this reference, the same as if set forth at length.

The invention claimed is:
 1. A method of treating a disease of therespiratory tract characterized by airway obstruction, comprisingadministering, to a subject in need thereof, an effective amount of acompound of formula (I) as an (−) enantiomer

wherein: n is 0 or 1; R1 and R2 may be the same or different, and areselected from the group consisting of: linear or branched C₁-C₆ alkyl,optionally substituted by one or more halogen atoms; —OR3 wherein R3 isa linear or branched C₁-C₆ alkyl optionally substituted with one or morehalogen atoms or C₃-C₇ cycloalkyl groups; and —NHSO₂R4 wherein R4 is alinear or branched C₁-C₄ alkyl optionally substituted with one or morehalogen atoms, wherein at least one of R1 and R2 is —NHSO₂R4, or apharmaceutically acceptable salt thereof.
 2. A method according to claim1, wherein R1 is —NHSO₂R4, wherein R4 is methyl, R2 is —OR3, wherein R3is cyclopropylmethyl, and n is
 0. 3. A method according to claim 1,wherein R1 is —NHSO₂R4, wherein R4 is methyl, R2 is —OR3, wherein R3 iscyclopropylmethyl, and n is
 1. 4. A method according to claim 1, whereinR1 is —OR3, R2 is —NHSO₂R4 wherein R4 is methyl, and n is
 1. 5. A methodaccording to claim 1, wherein R1 is methyl, R2 is —NHSO₂R4 wherein R4 ismethyl, and n is
 1. 6. A method according to claim 1, wherein both R1and R2 are —NHSO₂R4, wherein R4 is methyl, and n is
 0. 7. A methodaccording to claim 1, wherein both R1 and R2 are —NHSO₂R4, wherein R4 ismethyl, and n is
 1. 8. A method according to claim 1, further comprisingadministering a second pharmaceutical active component selected from thegroup consisting of a β2 agonist, an M3 antagonist, and acorticosteroid.
 9. A method according to claim 8, wherein said secondactive component is formoterol or carmoterol.
 10. A method according toclaim 1, comprising administering a pharmaceutical compositioncomprising a compound of formula (I) or a salt thereof and one or morepharmaceutically acceptable carriers and/or excipients.
 11. A methodaccording to claim 1, comprising administering a pharmaceuticalcomposition comprising: a compound of formula (I) or a salt thereof; asecond pharmaceutical active component selected from the groupconsisting of a β2 agonist, an M3 antagonist, and a corticosteroid; andone or more pharmaceutically acceptable carriers and/or excipients. 12.A method according to claim 10, wherein said administering is carriedout with a device which is a single- or multi-dose dry powder inhaler, ametered dose inhaler, or a soft mist nebulizer.
 13. A method accordingto claim 11, wherein said administering is carried out with a devicewhich is a single- or multi-dose dry powder inhaler, a metered doseinhaler, or a soft mist nebulizer.
 14. A method according to claim 1,wherein said disease of the respiratory tract characterized by airwayobstruction is asthma.
 15. A method of preventing and/or treating atopicdermatitis, comprising administering an effective amount of a compoundof formula (I) or a salt thereof according to claim 1, wherein saiddisease of the respiratory tract characterized by airway obstruction isCOPD.
 16. A method according to claim 2, wherein said disease of therespiratory tract characterized by airway obstruction is asthma.
 17. Amethod according to claim 2, wherein said disease of the respiratorytract characterized by airway obstruction is COPD.
 18. A methodaccording to claim 3, wherein said disease of the respiratory tractcharacterized by airway obstruction is asthma.
 19. A method according toclaim 3, wherein said disease of the respiratory tract characterized byairway obstruction is COPD.
 20. A method according to claim 4, whereinsaid disease of the respiratory tract characterized by airwayobstruction is asthma.
 21. A method according to claim 4, wherein saiddisease of the respiratory tract characterized by airway obstruction isCOPD.